Flashlights with a power switch and mechanisms to adjust the beam of light have been developed. For a couple examples, see the following U.S. Pat. Nos.: 5,158,358 and 4,916,588. These devices, however, have certain disadvantages. One disadvantage in many such devices is that they are awkward or impossible to turn on and focus without requiring two hands. This deficiency was recognized and some effort was made to resolve it.
U.S. Pat. No. 5,171,086 to Baloochi is an example of an effort to address some of the deficiencies. Baloochi shows a hand-held adjustable focus flashlight involving numerous parts and complexity, which typically translates into relatively high manufacturing costs and issues of reliability with all the moving parts. As another example of a complex attempt to address problems in creating a focusable flashlight for operation with one hand, some have proposed using devices with pinned cams that at the extremes operate the power switch and in intermediate positions use the cam to move the lamp relative to the reflector to focus the flashlight.